Method for molding objects of sponge rubber and the like



Nov. 14, 1950 w.1 COOK 2,530,289

- um'raon FOR MOLDING OBJECTS OF SPONGE RUBBER, AND THE LIKE 2 Sheets-Sheet 1 Filed Aug, 25, 1948 .ukiuwu w QBEQ$% I r v r J & a E e iqkwua l 4 Ow mm em. we 4m Z H 6 F K 1 W 3 W 2.9 ml 1m I i www I Q J L I sm mm 9 2 me iv bw 1 m 8 in EQREFQ \TN mm @C k D mm m IL -1 cm n o o: m: r m r $4 *1 3 T &\ in M in RN u mm i9 m NM Ev m i Nov. 14, I950 w. L. COOK 2,530,289

METHOD FOR MOLDING OBJECTS OF SPONGE RUBBER, AND THE LIKE Filed Aug. 25, 1948 2 Sheets-Sheet 2.

I 2'? hugzgq Patented Nov. 14, 1950 METHOD FOR MOLDING OBJECTS OF SPONGE RUBBER AND THE LIKE Wallace L. Cook, Chicago, Ill., assignor to The Whitney Blake Company, Hamden, Conn., a corporation of Connecticut Application August 25, 1948, Serial No. 46,158

3 Claims. 1

The present invention relates to improvements in the art of molding objects from expansible compounds such, for instance, as sponge rubber and the like, i. e., compounds which are (in their molded condition) expanded into cellular or porous structures.

In the art of molding objects from sponge rubber and the like, it has heretofore been the general practice to introduce into molding-cavities biscuits or charges of carefully-predetermined volume of the desired gas-expansible compounds prior to closing the mold-elements. Such biscuits or charges have been sufficiently smaller in volume than the volume provided by the given mold-cavity into which they are placed, to allow for the expansion of such charges when heated, under the action of the gas-producing materials included in the compound.

The above-outlined prior practice has been slow and cumbersome and hence expensive, since it has required the prior preparation of definite predetermined charges of compound and their individual placement in mold-cavities. Such procedure requires a relatively-long moldingcycle and hence ties up expensive molds and presses.

The main object of the present invention is to provide a superior method whereby objects of gas-expanded materials may be rapidly and economically produced without requiring the prior preparation of predetermined individual charges of material.

Another object of the present invention is toprovide a superior method whereby objects of sponge rubber and the like may be rapidly and economically produced by injecting the gas-expansible material into the mold-cavities after the elements making up the said mold-cavities are in their normally closed position.

With the above and other objects in view, as will appear to those skilled in the art from the present disclosure, this invention includes all features in the said disclosure which are novel over the prior art.

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

Fig. 1 is a schematic view illustrating an injection-molding apparatus suitable for carrying out the present invention;

Fig. 2 is a perspective view of the lower moldmember, displacement-slides, and related parts, and showing the said displacement-slides in their advanced position;

Fig. 3 is a broken sectional view taken on the line 3-3 of Fig. 2 and including the upper moldmember; and

Fig. 4 is a fragmentary view similar to Fig. 2 but showing the displacement-slides in their retired position.

The particular apparatus chosen for illustration in the accompanying drawings in order to make clear one mode of carrying out the present invention includes two complemental moldmembers which in the present instance comprise an upper mold-member generally designated by the reference character In anda lower moldmember generally designated by the reference character II.

In its upper face, the lower mold-member II is formed with two (more or less) molding-cavities !2--l2 which are shaped to conform to the desired shape of the object to be molded. In the present instance, the mold-cavities are of substantially-cylindrical form, though obviously they may assume other forms necessary to produce objects of an infinite number of other shapes, in accordance with well-known molding practice.

Spaced slightly from the molding-cavities I2 is a sprue-passage l3 which is connected to each of the molding-cavities l2 by one of two gatepassages [4. Leading substantially radially outwardly from each of the mold-cavities H2 in a direction away from the adjacent gate-passage M is one of two guide-grooves l5--l5 which at its outer end intersects a guide-groove It also formed in the upper face of the mold-member l I. The said guide-groove I6 extends at substantially a right angle with respect to the guide-grooves l5l 5 and accommodates with a close sliding fit, a reciprocating actuating-slide H having a rodlike extension [8 projecting from one of its ends. The said extension [8 is preferably formed of brass or other nonmagnetic material and carries at its extreme outer end a core 19 formed of soft iron or other suitable magnetic material and designed for purposes as will hereinafter appear.

The reciprocating actuating-slide I! above referred to is formed in its upper face with two interconnected recesses 20, in each of which is adapted to be received the outer end of one of two displacement-slides 2i2l. The said displacement-slides are respectively adapted to reciprocate in the adjacent radial guide-grooves l5l5 in the mold-member II. The respective outer wall of each of the recesses 20 contitutes a cam-surface 22 having a dwell 23, as is shown in Figs. 2 and 4.

The outer end of each of the displacementslides 2l-2l is provided with an antifriction roller 24 which is adapted to engage with the adjacent cam-surface 22 and with the dwell 23, in a manner as will hereinafter appear. The said roller is mounted for rotation upon a stud 25 to which is attached the inner end of a helical retracting-spring 26 which has its outer end anchored to a stud mounted in a suitable bracket 21 at the adjacent outer face of the mold-member ll. Each spring 26 serves, when permitted by the actuating-slide H, to outwardly retire the displacement-slide 21 to which it is attached.

The upper mold-member H above referred to is carried by the reciprocating crosshead 28 of a molding-press which may be of any suitable form. The said crosshead 28 is adapted to ride upon a suitable number of vertical tie-rods 29 and is advanced and retired by means of a piston 38 operating within a hydraulic cylinder 3i, as is indicated in Fig. l. The said cylinder is provided with two pipes or tubes 32 and 33 respectively located above and below the piston 3i? and respectively adapted to admit or exhaust fluid, whereby the said piston and the parts carried thereby may be moved in opposite directions, all in the manner well understood in the art.

The complemental lower mold-member H is supported upon the base 34 of the molding-press, which latter is connected to the cylinder 3| by means of the tie-rods 29 before referred to.

The mold-member l and the mold-member l I are jointly formed at their ends with a spherically-contoured socket 35 with which the spruepassage 13 in the mold-chamber ll connects. The said socket is adapted to receive the spherically-contoured outer end of a tubular injectionnozzle 36 which is adapted to reciprocate into and out of engagement with the said socket, in a manner as will hereinafter appear.

The injection-nozzle 36 above referred to is rigidly carried by a carriage 3'! mounted for reciprocation toward and away from the adjacent ends of the mold-members Ill and H, upon a base 38. Projecting upwardly from the end of the carriage 37 nearest the mold-members l0 and H are two rigid spaced-apart brackets 3939. Extending between and supported by the brackets 3938 is a piston-rod All which extends axially through a cylinder 4! and carries a piston 42 located within the said cylinder. The said cylinder 4| is rigidly carried at the upper end of a bracket 43, having its lower end rigidly secured to the stationary base 38, as is indicated in Fig. 1.

The opposite end-portions of the cylinder 4| are respectively connected by means of tubes or ducts M and 45 to the similar end-portions of a valve-housing 4B. Mounted for reciprocation within the valve-housing A8 is a reciprocating gate or slide All having operating-rods 48 and 49 respectively projecting from its opposite end through the adjacent end-walls of the said valvehousing 56, as is schematically indicated in Fig. 1. The operating-rods 48 and 9 are preferably formed of brass, bronze or other suitable nonmagnetic material and they respectively carry at their outer ends one of two cores 50 and formed of soft iron or other suitable magnetic material. The core 50 is adapted to operate within a solenoid-coil 52. Similarly, the core 5i is adapted to operate within a similar solenoidcoil 53. Substantially centrally, the valve-housing 46 above referred to has connected into it an inlet-tube 54 leading from a suitable source of fluid pressure, and an outlet-tube 55 leading to a suitable drain.

The injection-nozzle 36 before referred to is in tubular form and has an aperture 56 in one side with which communicates the lower end of a hopper 51 in which may be charged a suitable compound for forming sponge rubber or the like. Adapted to reciprocate within the hollow injection-nozzle 35 is a feed-plunger 58 which is coupled by means of a connecting-rod 59 to a piston 60. The said piston 60 is adapted to reciprocate in a cylinder 5| which is rigid with the carriage 3'! before referred to.

Respectively connected to the opposite endportions of the cylinder Bl are two tubes or ducts 62 and 63. The ends of the tubes 62 and 63 remote from the cylinder 6| extend into a valvehousing 64. Also communicating with the interior of the valve-housing 64 are an inlet-tube 65 and an outletetube 66 respectively leading from a source of hydraulic pressure and to a suitable drain, in a manner well understood in the art.

Mounted for reciprocation within the valvehousing-64 is a gate or slide 61 having operatingrods 68 and 69 respectively projecting from its opposite ends through the adjacent end-walls of the valve-housing B4. The said operating-rods 68 and 69 are preferably formed of nonmagnetic material and respectively carry at their outer ends cores N! and ll both formed of soft iron or other suitable magnetic material. The said cores Hi and H are adapted to reciprocate within solenoid-coils l2 and 13, all for purposes as will hereinafter appear.

In conjunction with the features above described, there i employed-a control-mechanism such as the control-mechanism shown at the lower right of Fig. 1, and which includes a plurality of contact-plates i4, 15, i6, 71, 18 and 79, all of which are adapted to be swept over by a brush-like switch-arm 80. In the instance shown the contact-armtfl is carried by a rotary gearwheel 3| which is formed of insulating material and which is meshed into and driven by a drivepinion 82 forming a feature of a synchronous electric motor 83 or other suitable timing device.

The crosshead 28 of the molding-press carries a contact-plate 84 which is adapted to engage and electrically interconnect two contacts respectively numbered 85 and 86 when the said crosshead 28 is moved toward the mold-member H to engage the mold-member l9 therewith, as is indicated in Fig. l. The contact'85 just referred to is connected by means of a wire 81 to a main-line wire 88, which latter is a companion to another main-line wire 89. Both of the said main-line wires lead from any suitable source of electric current. The remainin contact 86 is connected by means of a wire to one terminal of the synchronous electric motor 83. The wire 90 is connected by means of a branch wire 9| to the switch-arm 89 located adjacent the motor 83.

From the foregoing it will be seen that the switch comprising the elements 84, 85 and 86 controlled by the movement of the crosshead 28 of the molding-press, controls the flow of current to the synchronous electric motor 83 and also to the switch-arm 88 and, therefore, to all the contacts 'Mto l9 inclusive and the features connected therewith.

The main-line wire 89 is connected by means of a wire 92 to the remaining terminal of the synchronous electric motor 83, all as is indicated in Fig. l. The wire 92 has connected into it a wire 93 leading to one terminal of each of two solenoid-coils 94 and 95 respectively adapted to have the core I9. extend. thereinto. The remaining ber Ii.

terminal of the solenoid-coil 94 is connected by means of a wire 95 to the contact-plate 18 which is located adjacent the synchronous electric motor 83. The remaining terminal of the companion solenoid-coil 95 is connected by means of a wire 91 to the contact-plate I5.

The contact-plate I4 adjacent the motor 83 is connected by means of a wire 98 to one terminal of the solenoid-coil 52. The remaining terminal of the said solenoid-coil 52 is connected by means of a wire 99 to the wire 92 and hence to the main-line wire 89,

The contact-plate 16 adjacent the motor 83 is connected by means of a wire I88 to one terminal of the solenoid-coil I2, which latter has its remaining terminal connected by means of a wire I8I to the wire 99 before referred to.

The contact-plate 1'! adjacent the motor 83 is connected by means of a wire I82 toone terminal of the solenoid-coil I3 previously described. The remaining terminal of the said solenoid-coil I3 is connected directly to the wire 99 before referred to. The contact-plate I9 of the control-mechanismis connected by means of a wire I83 to one terminal of I the solenoid-coil 53, which latter has its remainingterminal connected by rneans of a wire Ill to the wire 88 previously referred to. The gas-egpansiblecompounds suitable for use in the apparatus above described'arevery numerous, but the following compounds (parts'by weight) maybe mentioned by way of example;

Pale Crepe Rubber Butadiene-Styrcne Oopolymer (GR-S) Cgi/lloroprene Polymer (Neoprene GR- -Zi nc Salt of Xylyl Mercaptan (RPA No. 5) 50% with 50% Solvent such as Kerosene Zinc Oxide Light Calcined Magnesia; Fine Carbon Black Coarse Carbon Black Calcium Carbonate Sodium Bicarbonate Mixture of 40 parts of Di Nitroso Ienta Methylene Tetrarnine Dispersed in 60 parts of Inert Inorganic Filler such as Clay (Unicel ND Etearic Ar-id' Refined Petroleum Oil (Nujol) Petrolatum Condensation Product of Bntyraldehyde and Aniline (Ant0x) Phxenyl Alpha Napthylamine (Neozone 1 Tetra Methy1 Thiuram Mono Sulfide (Thionex) 0. 1875 0. Sulfur 50 3 Salicylic Acid (Retardcr W) l Mercapto Benzothiazyl D1sulfide Sodium Acetate.

Operation For purposes of description, let it be assumed that the crosshead 28 of the press is raised so as to leave a space between the mold-members I8 and II and, further, that the injection-nozzle 35 is retired away from the said mold-members and that the displacement-slides are retired into the positions indicated in Fig. 4.

Now, when hydraulicpressure from any suitable source is fed mic the upper portion of the cylinder 3!, the 'piston'iiil will be moved downwardly into the position'in which it is shown in Fig. Ito thus 'engagethe underface of the moldmember I8 with the upper face of the mold-mem- The movement of the crosshead 28 just described will also engage the contact-plate 83 with the contacts 85 and 86 thereby supplying current to both the switch-arm 88 and the synchronous electric motor 83, which latter will imtaneously engage with the contact-plates Hand I5therebyenergizing the solenoid-coil 52 and the solenoid-coil 95. g 3 I 'The energization of the solenoid-coil 52 will cause the core 58 to be drawn into the position in which it is indicated inFig. 1 to thereby shift the gate or slide 41 into position to supply hy draulic pressure through the tube 45 to theright end-portion of the cylinder 4|. The hydraulic pressure will move the piston 42 from right to left and thus move the carriage 31 in a similar direction to seat the end of the injection-nozzle 36 in the socket 35 provided jointly in theadjacent ends of the mold-members I0 and II.

The energization of the solenoid-coil will cause the core I9 to move from left to right, thus similarly moving the actuating-slide 11. The said movement of the actuating-slide II .will, in turn, cause its cam-surfaces 2222 to advance the displacement-slides 2I2I into their respective molding-cavities I2l2 to thus reduce, for the timebeing, the volumetric capacities of the said mold-cavities. The respective rollers 24 of the displacement-slides 2|2I will, under the present circumstances, come to rest upon the adjacent dwells 2323 until such time as the actuating-slide IT is moved in an opposite direction. The mechanism is now in condition for the injection of sponge rubber or similar compounds into the molding-cavities I2I2.

After having engaged the contact-plates "I4 and I5 as above described, the switch-blade 88 will engage the contact-plate I5, thereby energizing the solenoid-coil I2 to thus bring the core 10 into the position in which it is indicated in Fig. 1. The described movement of the'core ID will also shift the gate or slide 61' into the position in which it is indicated in Fig. l. Thedescribed movement of the gate or slide 6! will serve to supply hydraulic pressure to the right end of the cylinder 6|, thereby forcing the piston 60 from. right to left to thus. similarly move the feed-plunger 58.; The movement-of the feedplunger 58 will cause the desired amount of BX? pansible compound to be rapidly injected through the sprue-passage I3 and gate-passages I I-I4 into both of the molding-cavities I2-I2 while the same have their volumetric capacities re duced by the inward position of the displacement-slides 2I2|; connection, that under the present circumstances, the mold-members In and l I would be pre-heated by any suitable means and kept at an elevated temperature, in accordance with'usual practice. After having engaged the contact-plate I6, the switch-arm 88 will next engage the contactplate II, thereby energizing the solenoid-coil I3, while the injection-nozzle 36 is still in its advanced position and while the mold-members I8 and I I are still in engagement. The energization of the solenoid-coil I3 will pull the core II from left to right,'thereby similarly shifting the gate or slide 81. The described shifting of the gate or slide 6! will vent the right end of the cylinder 6| and immediately supply hydraulic pressure to the left end of the cylinder 6| with the effect of retracting the feed-plunger 58. Immediately following the retraction of the f eed-plunger 58, the switch-arm 88 will substantially simultaneouslyI engage with both of the contact-plates I8 and. 9.

It may be explained, in this 7 The engagement'of the switch-arm 80 with the contact-plate 18 as described, will energize the solenoid-coil 94, with the effect of drawing the core 19 from right to left and similarly moving the actuating-slide I l. The described movement of the actuating-slide I l will permit the retracting-springs 2626 to retire their respective displacement-slides 2 l--2-l until (as is preferred) the respective inner surfaces of the said displacement-slides coincide with the lateralwalls of their respective molding-cavities l2-'|2', as is indicated in Fig. 4. The described retirement of the displacement-slides 2|2'lwill permit the compound previously injected into the molding-cavities to expand to fill the now increased volumet- I ric capacity of the latter.

' Substantially simultaneously with itsengagement with the contact-plate 78, the switch-arm 80- will also engage the contact-plate 19, as above described, to thereby energize the solenoid-coil 53. The energization of the solenoid-coil 53'Will draw the gate or slide ll-from left to right, thereby coincidentally exhausting the right endof the cylinder M and supplying hydraulic fluid to the left portion of the said cylinder. The hydraulic fluid will now move the piston 42 from left to right, to thus retract the carriage 3 and retire the injection-nozzle 33 out of engagement with the socket 35 in'the adjacent ends of the respective mold-members t0 and its After the completion of the cycle just referred to, the mold-members l0 and l I may be left closed for a desired length of time to effect vulcanization or other desired reaction. As soon as hydraulic pressure is supplied to the lower portion of the cylinder 3| through the tube 33,the mold member HJ- will be lifted to thus permit the newly-molded articles to be removed from the molding-cavities l2l2 and also to disengage the contact-plate 84 from the: contacts 85 and 86, to thus stop the synchronous electric motor 83-.

Another complete cycle like that above describetLmay be initiated by again lowering the mold-member J 0', as previously described, in connection with the'first-described cycle.

It willbe apparent from. the foregoing that the injection of" the selected expansible compound into the mold-cavities !.2--l2' or their equivalent,

is effected While the volumetric capacity thereof is reduced by the. displacement-slides 2l- ,2l being in; their advanced positions. It will further be apparent that immediately following the injection of the desiredrexpansible molding; material and after the cessation of injection pressure, the volumetric capacity of the said molding-cavities |2li2 is immediately increased-- to its in.- tended maximum, to thereby permit the expansible material to swell and fill the entire cavities.

The invention may be carried outv in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning. and equivalency range of the appended claims are intended to be embraced therein.

I claim:

1.x The method for molding porous or cellular objects of sponge rubber or the like, including the steps of preparing a mixture of gas-expansible molding material having gas-producing material intermixed there-with; reducing the volumetric capacity of a molding-cavity; thereafter injecting the said gas-expansiblemolding material together with its said gas-producing material into the said molding-cavity while the latter has its volumetric capacity reduced; subsequently to the said injection, expanding the volumetric capacity of the said molding-cavity while maintaining the latter closed; and causing the injected molding material to be expanded by its intermixed gasproducing material into a porous or cellular condition in the now-expandedmolding-cavity.

2. The method for molding porous or cellular objects of sponge rubber or the like, including the steps of: preparing a mixture of'gas-expansible molding material having gas-producing material intermixed therewith; reducing the volumetric capacity of a molding-cavity by temporarily projecting displacement-means thereinto; thereafter injecting the said gas-expansible molding material together with its intermixed gas-producing material into the said molding-cavity while the said displacement-means is projected thereinto; subsequently to the said injection, retiring the said displacement-means to expand the volumetric capacityof the said moldingcavity While still maintaining the latter closed; and causing the injected molding material to be expanded by its intermixed gas-producing material into a porous or cellular condition in the nowexpanded molding-cavity.

3. The method for molding porous or cellular objects of sponge rubber or the like, including the steps of; preparing a mixture of gas-expansible molding material having gas-producing material intermixed therewith; reducing the volumetric capacity of a molding-cavity by temporarily projecting displacement-means thereinto; thereafter'injecting the said gas-expansible molding material together with its intermixed gas-producing material into the said moldingcavity while the said displacement-means is projected thereinto; subsequently to the said injection, retiring the said displacement-means into a position to form part of the surface of the said molding-cavity and to expand the volumetric capacity of the said molding-cavity while maintaining the latter closed; and causing the injected molding material to be expanded by its intermixed gas-producing material into a porous or cellular condition in the now-expanded molding"- cavity.

7 .WALLACE L. COOK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,298,716 Moreland' et al Oct. 13, 1942 2,308,971 Carter Jan. 19, 1943 2,331,687 Hobson Oct. 12, 1943 2,331,688 Hobson Oct. 12, 1943 2,372,695 Taylor Apr. 3, 1945 

